Controlling multiple modems in a wireless terminal using dynamically varying modem transmit power limits

ABSTRACT

A mobile wireless terminal (MWT) includes multiple wireless modems. The multiple modems have their respective transmit outputs combined together to produce an aggregate transmit output. The multiple modems can concurrently transmit data in a reverse link direction and receive data in a forward link direction. The MWT is constrained to operate under an aggregate transmit power limit. Each of the multiple modems has an individual transmit limit related to the aggregate transmit power limit. An MWT controller adjusts the individual transmit power limits in the multiple modems based on an aggregate transmit power limit of the MWT and respective transmit power estimates from the modems, to cause each individual transmit power limit to track a corresponding individual modem transmit power.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is related to commonly-owned applications, filedconcurrently herewith, entitled “Wireless Terminal Operating Under AnAggregate Transmit Power Limit Using Multiple Modems Having FixedIndividual Transmit Power Limits” having application number (to beassigned, attorney docket number 010443), and “Controlling MultipleModems In A Wireless Terminal Using Energy-Per-Bit Determinations”having application number (to be assigned, attorney docket number020761), which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] I. Field of the invention

[0003] The present invention relates generally to mobile wirelessterminals, and particularly, to mobile wireless terminals havingmultiple modems which are constrained to operate under an aggregatetransmit power limit for all of the modems.

[0004] Ii. Related art

[0005] In a data call established between a mobile wireless terminal(mwt) and a remote station, the mwt can transmit data to the remotestation over a “reverse” communication link. Also, the mwt can receivedata from the remote station over a “forward” communication link. Thereis an ever pressing need to increase the transmit and receive bandwidth,that is, the data rates, available over both the forward and reverselinks.

[0006] Typically, the mwt includes a transmit power amplifier topower-amplify a radio frequency (rf) input signal. The power amplifierproduces an amplified, rf output signal having an output powerresponsive to the input power of the input signal. An inordinately highinput power may over-drive the power amplifier, and thus cause theoutput power to exceed an acceptable operating transmit power limit ofthe power amplifier. In turn, this may cause undesired distortion of theRF output signal, including unacceptable out-of-band RF emissions.Therefore, there is a need to carefully control the input and/or outputpower of the transmit power amplifier in an MWT so as to avoidover-driving the power amplifier. There is a related need to control theoutput power as just mentioned, while minimizing to the extent possible,any reduction of the forward and reverse link bandwidth (that is, datarates).

SUMMARY OF THE INVENTION

[0007] A feature of the present invention is to provide an MWT thatmaximizes an overall communication bandwidth in both the reverse andforward link directions using a plurality of concurrently operatingcommunication links, each associated with a respective one of aplurality of modulator-demodulators (modems) of the MWT.

[0008] Another feature of the present invention is to provide an MWTthat combines multiple modulator-demodulator (modem) transmit signalsinto an aggregate transmit signal (that is, an aggregate reverse linksignal) so that a single transmit power amplifier can be used. Thisadvantageously reduces power consumption, cost, and space requirementscompared to known systems using multiple power amplifiers.

[0009] Another feature of the present invention is to carefully controlan aggregate input and/or output power of the transmit power amplifier,thereby avoiding signal distortion at the power amplifier output. Arelated feature is to control the aggregate input and/or output power insuch a manner as to maximize bandwidth (that is, data through-put) inboth the reverse and forward link directions.

[0010] These features are achieved in several ways. First, individualtransmit power limits are established in each of the plurality of modemsof the MWT, to limit the respective, individual modem transmit powers.Each individual transmit power limit is derived, in part, from anaggregate transmit power limit for all of the modems. Together, theindividual transmit power limits collectively limit the aggregatetransmit power of all of the modems.

[0011] Second, the present invention adjusts the individual transmitpower limits in the modems of the MWT based on the aggregate transmitpower limit and respective transmit power estimates from the modems, tocause each individual modem transmit power limit to track acorresponding individual modem transmit power. To do this, the presentinvention collects and/or determines modem transmit statisticscorresponding to a previous transmit period or cycle of the MWT. Themodem transmit statistics can include individual modem transmit datarates, individual modem transmit powers, the aggregate transmit datarate of all of the modems, and an aggregate transmit power for all ofthe modems combined.

[0012] The invention also detects over-limit ones (that is, over-limitindividual members) of the modems. An over-limit modem has an actualtransmit power, or alternatively, a required transmit power, thatexceeds the individual transmit power limit established in the modem. Inresponse to detecting an over-limit modem, the present inventiondetermines new individual modem transmit power limits across the modemsusing the collected statistics, and updates the modems with the newtransmit power limits. The new transmit power limits are calculated soas to avoid over-limit conditions in the modems. The new modem limitsare used in a next transmit cycle of the MWT. The invention repeats theprocess periodically, to update the individual transmit limits overtime.

[0013] In the present invention, only active modems are scheduled totransmit data in the reverse link direction. “Inactive” modems aremodems that are not scheduled to transmit data. However, in the presentinvention, inactive modems are able to receive data in the forward linkdirection, thereby maintaining a high forward link through-put in theMWT, even when modems are inactive in the reverse link direction.

[0014] The present invention is directed to a method of controllingtransmit power in a data terminal having N wireless modems with theirrespective transmit outputs combined to produce an aggregate transmitoutput, comprising establishing an individual transmit power limit ineach of the N modems, scheduling each of a plurality of the N modems totransmit respective data, receiving a respective, reported transmitpower estimate from each of the N modems, and adjusting the individualtransmit power limits in at least some of the N modems based on theaggregate transmit power limit and the respective transmit powerestimates from the N modems. This causes each individual transmit powerlimit to track a corresponding individual modem transmit power.

[0015] The present invention is also directed to an MWT, constrained tooperate within an aggregate transmit power limit, including a plurality(N) of wireless modems with their respective transmit outputs combinedto produce an aggregate transmit output. The N modems can concurrentlytransmit data in the reverse link direction and receive data in theforward link direction. One aspect of the present invention is apparatuscomprising means for establishing an individual transmit power limit ineach of the N modems, means for scheduling each of a plurality of the Nmodems to transmit respective data, means for receiving a respective,reported transmit power estimate from each of the N modems, and meansfor adjusting the individual transmit power limits in at least some ofthe N modems based on the aggregate transmit power limit and therespective transmit power estimates from the N modems.

[0016] In further aspects, a method and apparatus is provided forderiving modem transmit limits in a wireless terminal constrained tooperate within an aggregate transmit power limit, the wireless terminalincluding N wireless modems with their respective transmit outputscombined to produce an aggregate transmit output, the modems havingindividual transmit power limits to limit their respective transmitpowers, the modems reporting respective transmit power estimates. Theapparatus comprises means for determining an aggregate transmit powerencompassing all of the N modems, means for deriving an aggregatetransmit power margin based on a difference between the aggregatetransmit power and the aggregate transmit power limit, and means fordividing the aggregate transmit power margin among the N modems toproduce, for each of the N modems, an individual transmit power limitthat is greater than the corresponding transmit power estimate for eachmodem. This and further aspects of the present invention are describedbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The features, objects, and advantages of the present inventionwill become more apparent from the detailed description set forth belowwhen taken in conjunction with the drawings in which like referencecharacters identify the same or similar elements throughout and wherein:

[0018]FIG. 1 is an illustration of an example wireless communicationsystem.

[0019]FIG. 2 is a block diagram of an example mobile wireless terminal.

[0020]FIG. 3 is a block diagram of an example modem representative ofindividual modems of the mobile wireless terminal of FIG. 2.

[0021]FIG. 4 is an illustration of an example data frame that may betransmitted or received by any one of the modems of FIGS. 2 and 3.

[0022]FIG. 5 is an illustration of an example status report from themodems of FIGS. 2 and 3.

[0023]FIG. 6 is a flowchart of an example method performed by each ofthe modems of FIGS. 2 and 3.

[0024]FIG. 7 is a flowchart of an example method performed by the mobilewireless terminal.

[0025]FIG. 8 is a flowchart expanding on the method of FIG. 7.

[0026]FIG. 9 is a flowchart expanding on the method of FIG. 7.

[0027]FIG. 10 is a flowchart of another example method performed by themobile wireless terminal.

[0028]FIG. 11 is an example plot of Power versus Modem index(i)identifying respective ones of the modems of FIG. 2, wherein uniformmodem transmit power limits are depicted. FIG. 11 also represents anexample transmit scenario of the mobile wireless terminal of FIG. 2.

[0029]FIG. 12 is another example transmit scenario similar to FIG. 11.

[0030]FIG. 13 is an illustration of an alternative, tapered arrangementfor the modem transmit power limits.

[0031]FIG. 14 is a flowchart of an example method of calibrating modemsin the mobile wireless terminal of FIG. 2.

[0032]FIG. 15 is a flowchart of an example method of operating themobile wireless terminal, using dynamically updated individual modemtransmit power limits.

[0033]FIG. 16 is a flowchart of an example method expanding on themethod of FIG. 15.

[0034]FIG. 17 is a flowchart of an example method of determining amaximum number of active modems using an averageenergy-per-transmitted-bit of the modems.

[0035]FIG. 18 is a flowchart of an example method of determining amaximum number of active modems, using an individualenergy-per-transmitted-bit for each of the modems.

[0036]FIG. 19 is a graphical representation of different modem transmitlimit arrangements.

[0037]FIG. 20 is a flowchart of an example method of operating themobile wireless terminal using dynamically varying individual modemtransmit power limits, so the modem transmit limits track the modemtransmit powers.

[0038]FIG. 21 is a flow chart of an example method expanding on themethod of FIG. 20.

[0039]FIG. 22 is a flow chart of an example method expanding on themethod of FIG. 21.

[0040] FIGS. 23A-23D are example plots of power versus modem indexidentifying modems being controlled in accordance with the method ofFIG. 20, for different example transmit scenarios of the mobile wirelessterminal of FIG. 2.

[0041]FIG. 24 is a functional block diagram of an example controller ofthe mobile wireless terminal of FIG. 2, for performing the methods ofthe present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0042] A variety of multiple access communication systems and techniqueshave been developed for transferring information among a large number ofsystem users. However, spread spectrum modulation techniques, such asthose used in code division multiple access (CDMA) communication systemsprovide significant advantages over other modulation schemes, especiallywhen providing service for a large number of communication system users.Such techniques are disclosed in the teachings of U.S. Pat. No.4,901,307, which issued Feb. 13, 1990 under the title “Spread SpectrumMultiple Access Communication System Using Satellite or TerrestrialRepeaters,” and U.S. Pat. No. 5,691,174, which issued Nov. 25, 1997,entitled “Method and Apparatus for Using Full Spectrum Transmitted Powerin a Spread Spectrum Communication System for Tracking IndividualRecipient Phase Time and Energy,” both of which are assigned to theassignee of the present invention, and are incorporated herein byreference in their entirety.

[0043] The method for providing CDMA mobile communications wasstandardized in the United States by the Telecommunications IndustryAssociation in TIA/EIA/IS-95-A entitled “Mobile Station-Base StationCompatibility Standard for Dual-Mode Wideband Spread Spectrum CellularSystem,” referred to herein as IS-95. Other communications systems aredescribed in other standards such as the IMT-2000/UM, or InternationalMobile Telecommunications System 2000/Universal MobileTelecommunications System, standards covering what are referred to aswideband CDMA (WCDMA), cdma2000 (such as cdma2000 1× or 3× standards,for example) or TD-SCDMA.

[0044] I. Example Communication Environment

[0045]FIG. 1 is an illustration of an exemplary wireless communicationsystem (WCS) 100 that includes a base station 112, two satellites 116 aand 116 b, and two associated gateways (also referred to herein as hubs)120 a and 120 b. These elements engage in wireless communications withuser terminals 124 a, 124 b, and 124 c. Typically, base stations andsatellites/gateways are components of distinct terrestrial and satellitebased communication systems. However, these distinct systems mayinter-operate as an overall communications infrastructure.

[0046] Although FIG. 1 illustrates a single base station 112, twosatellites 116, and two gateways 120, any number of these elements maybe employed to achieve a desired communications capacity and geographicscope. For example, an exemplary implementation of WCS 100 includes 48or more satellites, traveling in eight different orbital planes in LowEarth Orbit (LEO) to service a large number of user terminals 124.

[0047] The terms base station and gateway are also sometimes usedinterchangeably, each being a fixed central communication station, withgateways, such as gateways 120, being perceived in the art as highlyspecialized base stations that direct communications through satelliterepeaters while base stations (also sometimes referred to ascell-sites), such as base station 112, use terrestrial antennas todirect communications within surrounding geographical regions.

[0048] User terminals 124 each have or include apparatus or a wirelesscommunication device such as, but not limited to, a cellular telephone,wireless handset, a data transceiver, or a paging or positiondetermination receiver. Furthermore each of user terminals 124 can behand-held, portable as in vehicle-mounted (including for example cars,trucks, boats, trains, and planes), or fixed, as desired. For example,FIG. 1 illustrates user terminal 124 a as a fixed telephone or datatransceiver, user terminal 124 b as a hand-held device, and userterminal 124 c as a portable vehicle-mounted device. Wirelesscommunication devices or terminals 124 are also sometimes referred to asmobile wireless terminals, user terminals, mobile wireless communicationdevices, subscriber units, mobile units, mobile stations, mobile radios,or simply “users,” “mobiles,” “terminals,” or “subscribers” in somecommunication systems, depending on preference.

[0049] User terminals 124 engage in wireless communications with otherelements in WCS 100 through CDMA communications systems. However, thepresent invention may be employed in systems that employ othercommunications techniques, such as time division multiple access (TDMA),and frequency division multiple access (FDMA), or other waveforms ortechniques listed above (WCDMA, CDMA2000 . . . ).

[0050] Generally, beams from a beam source, such as base station 112 orsatellites 116, cover different geographical areas in predefinedpatterns. Beams at different frequencies, also referred to as CDMAchannels, frequency division multiplexed (FDM) channels, or “sub-beams,”can be directed to overlap the same region. It is also readilyunderstood by those skilled in the art that beam coverage or serviceareas for multiple satellites, or antenna patterns for multiple basestations, might be designed to overlap completely or partially in agiven region depending on the communication system design and the typeof service being offered, and whether space diversity is being achieved.

[0051]FIG. 1 illustrates several exemplary signal paths. For example,communication links 130 a-c provide for the exchange of signals betweenbase station 112 and user terminals 124. Similarly, communications links138 a-d provide for the exchange of signals between satellites 116 anduser terminals 124. Communications between satellites 116 and gateways120 are facilitated by communications links 146 a-d.

[0052] User terminals 124 are capable of engaging in bi-directionalcommunications with base station 112 and/or satellites 116. As such,communications links 130 and 138 each include a forward link and areverse link. A forward link conveys information signals to userterminals 124. For terrestrial-based communications in WCS 100, aforward link conveys information signals from base station 112 to a userterminal 124 over a link 130. A satellite-based forward link in thecontext of WCS 100 conveys information from a gateway 120 to a satellite116 over a link 146 and from the satellite 116 to a user terminal 124over a link 138. Thus, terrestrial-based forward links typically involvea single wireless signal path between the user terminal and basestation, while satellite-based forward links typically involve two ormore wireless signal paths between the user terminal and a gatewaythrough at least one satellite (ignoring multipath).

[0053] In the context of WCS 100, a reverse link conveys informationsignals from a user terminal 124 to either a base station 112 or agateway 120. Similar to forward links in WCS 100, reverse linkstypically require a single wireless signal path for terrestrial-basedcommunications and two wireless signal paths for satellite-basedcommunications. WCS 100 may feature different communications offeringsacross these forward links, such as low data rate (LDR) and high datarate (HDR) services. An exemplary LDR service provides forward linkshaving data rates from 3 kilobits per second (kbps) to 9.6 kbps, whilean exemplary HDR service supports typical data rates as high as 604 kbpsand higher.

[0054] As described above, WCS 100 performs wireless communicationsaccording to CDMA techniques. Thus, signals transmitted across theforward and reverse links of links 130, 138, and 146 convey signals thatare encoded, spread, and channelized according to CDMA transmissionstandards. In addition, block interleaving can be employed for theseforward and reverse links. These blocks are transmitted in frames havinga predetermined duration, such as 20 milliseconds.

[0055] Base station 112, satellites 116, and gateways 120 may adjust thepower of the signals that they transmit over the forward links of WCS100. This power (referred to herein as forward link transmit power) maybe varied according to user terminal 124 and according to time. Thistime varying feature may be employed on a frame-by-frame basis. Suchpower adjustments are performed to maintain forward link bit error rates(BER) within specific requirements, reduce interference, and conservetransmission power.

[0056] User terminals 124 may adjust the power of the signals that theytransmit over the reverse links of WCS 100, under the control ofgateways 120 or base stations 112. This power (referred to herein asreverse link transmit power) may be varied according to user terminal124 and according to time. This time varying feature may be employed ona frame-by-frame basis. Such power adjustments are performed to maintainreverse link bit error rates (BER) within specific requirements, reduceinterference, and conserve transmission power.

[0057] Examples of techniques for exercising power control in suchcommunication systems are found in U.S. Pat. No. 5,383,219, entitled“Fast Forward Link Power Control In A Code Division Multiple AccessSystem,” U.S. Pat. No. 5,396,516, entitled “Method And System For TheDynamic Modification Of Control Parameters In A Transmitter PowerControl System,” and U.S. Pat. No. 5,056,109, entitled “Method andApparatus For Controlling Transmission Power In A CDMA Cellular MobileTelephone System,” which are incorporated herein by reference.

[0058] II. Mobile Wireless Terminal

[0059]FIG. 2 is a block diagram of an example MWT 206 constructed andoperated in accordance with the principles of the present invention. MWT206 communicates wirelessly with a base station or gateway (referred toas a remote station), not shown in FIG. 2. Also, MWT 206 may communicatewith a user terminal. MWT 206 receives data from external datasources/sinks, such as a data network, data terminals, and the like,over a communication link 210, such as an ethernet link, for example.Also, MWT 206 sends data to the external data sources/sinks overcommunication link 210.

[0060] MWT 206 includes an antenna 208 for transmitting signals to andreceiving signals from the remote station. MWT 206 includes a controller(that is, one or more controllers) 214 coupled to communication link210. Controller 214 exchanges data with a memory/storage unit 215, andinterfaces with a timer 217. Controller 214 providesdata-to-be-transmitted to, and receives data from, a plurality ofwireless modems 216 a-216 n over a plurality of correspondingbi-directional data links 218 a-218 n between controller 214 and modems216. Data connections 218 may be serial data connections. The number Nof modems that may be used can be one of several values, as desired,depending on known design issues such as complexity, cost, and so forth.In an example implementation, N=16.

[0061] Wireless modems 216 a-216 n provide RF signals 222 a _(T)-222 n_(T) to and receive RF signals 222 a _(R)-222 n _(R) from a powercombiner/splitter assembly 220, over a plurality of bi-directional RFconnections/cables between the modems and the power combiner/splitterassembly. In a transmit (that is, reverse link) direction, a powercombiner included in assembly 220 combines together the RF signalsreceived from all of modems 216, and provides a combined (that is,aggregate) RF transmit signal 226 to a transmit power amplifier 228.Transmit power amplifier 228 provides an amplified, aggregate RFtransmit signal 230 to a duplexer 232. Duplexer 232 provides theamplified, aggregate RF transmit signal to antenna 208. In MWT 206,duplexing may be achieved by means other than duplexer 232, such asusing separate transmit and receive antennas. Also, a power monitor 234,coupled to an output of power amplifier 228, monitors a power level ofamplified, aggregate transmit signal 230. Power monitor 234 provides asignal 236 indicating the power level of amplified, aggregate transmitsignal 230 to controller 214. In an alternative arrangement of MWT 206,power monitor 234 measures the power level of aggregate signal 226 atthe input to transmit amplifier 228. In this alternative arrangement,the aggregate transmit power limit of MWT 206 is specified at the inputto transmit amplifier 228 instead of at its output, and the methods ofthe present invention, described below, take this into account.

[0062] In a receive (that is, forward link) direction, antenna 208provides a received signal to duplexer 232. Duplexer 232 routes thereceived signal to a receive amplifier 240. Receive amplifier 240provides an amplified received signal to assembly 220. A power splitterincluded in assembly 220 divides the amplified received signal into aplurality of separate received signals and provides each separate signalto a respective one of the modems 216.

[0063] MWT 206 communicates with the remote station over a plurality ofwireless CDMA communication links 250 a-250 n established between MWT206 and the remote station. Each of the communication links 250 isassociated with a respective one of modems 216. Wireless communicationlinks 250 a-250 n can operate concurrently with one another. Each ofwireless communication links 250 supports wireless traffic channels forcarrying data between MWT 206 and the remote station in both forward andreverse link directions. The plurality of wireless communicationchannels 250 form part of an air interface 252 between MWT 206 and theremote station.

[0064] In the present embodiment, MWT 206 is constrained to operateunder an aggregate transmit power limit (APL) at the output of transmitamplifier 228. In other words, MWT 206 is required to limit the transmitpower of signal 230 to a level that is preferably below the aggregatetransmit power limit. All of modems 216, when transmitting, contributeto the aggregate transmit power of signal 230. Accordingly, the presentinvention includes techniques to control the transmit powers of modems216, and thereby cause the aggregate transmit power of modems 216, asmanifested in transmit signal 230, to be under the aggregate transmitpower limit.

[0065] Over-driving transmit amplifier 228 causes the power level ofsignal 230 to exceed the aggregate transmit power limit. Therefore, thepresent invention establishes individual transmit power limits (alsoreferred to as transmit limits) for each of modems 216. The individualtransmit power limits are related to the aggregate transmit power limitin such a way as to prevent modems 216 from collectively over-drivingtransmit amplifier 228. During operation of MWT 206, the presentinvention detects over-limit ones of modems 216. In response todetecting the over-limit modem(s), controller 214 adjusts the individualtransmit power limits in at least some of modems 216 based on theaggregate transmit power limit and respective transmit power estimatesfrom modems 216, to cause each individual modem transmit power limit totrack a corresponding individual modem transmit power. An objective isto maximize bandwidth (that is, transmit data rate) for a givenaggregate transmit power limit by adjusting the individual modemtransmit power limits. Further aspects of the present invention aredescribed below.

[0066] Although MWT 206 is referred to as being mobile, it is to beunderstood that the MWT is not limited to a mobile platform or portableplatforms. For example, MWT 206 may reside in a fixed base station orgateway. MWT 206 may also reside in a fixed user terminal 124 a.

[0067] III. Modem

[0068]FIG. 3 is a block diagram of an example modem 300 representativeof each of modems 216. Modem 300 operates in accordance with CDMAprinciples. Modem 300 includes a data interface 302, a controller 304, amemory 306, a modem signal processor or module 308, such as one or moredigital signal processors (DSP) or ASICs, an intermediate frequencyIF/RF subsystem 310, and an optional power monitor 312, all coupled toone another over a data bus 314. In some systems, the modems do notcomprise transmit and receive processor coupled in pairs as in a moretraditional modem structure, but may use an array of transmitters andreceivers or modulators and demodulates which are interconnected asdesired to handle user communications, and one or more signals, orotherwise time shared among users.

[0069] In the transmit direction, controller 304 receivesdata-to-be-transmitted from controller 214 over data connection 218 i(where i indicates any one of the modems 216 a-216 n), and throughinterface 302. Controller 304 provides the data-to-be-transmitted tomodem processor 308. A transmit (Tx) processor 312 of modem processor308 encodes and modulates the data-to-be-transmitted, and packages thedata into data frames that are to be transmitted. Transmit processor 312provides a signal 314 including the data frames to IF/RF subsystem 310.Subsystem 310 frequency up-converts and amplifies signal 314, andprovides a resulting frequency up-converted, amplified signal 222 _(T)to power combiner/splitter assembly 220. Optional power meter 312monitors a power level of signal 222 i _(T) (that is, the actualtransmit power at which modem 300 transmits the above-mentioned dataframes). Alternatively, modem 300 can determine the modem transmit powerbased on gain/attenuator settings of IF/RF subsystem 310 and the datarate at which modem 300 transmits the data frames.

[0070] In the receive direction, IF/RF subsystem 310 receives a receivedsignal 222 i _(R) from power combiner/splitter assembly 220, frequencydown-converts signal 222 i _(R) and provides the resulting frequencydown-converted signal 316, including received data frames, to a receive(Rx) processor 318 of modem processor 308. Receive processor 318extracts data from the data frames, and then controller 304 provides theextracted data to controller 214, using interface 302 and dataconnection 218 i.

[0071] Modems 216 each transmit and receive data frames in the mannerdescribed above and further below. FIG. 4 is an illustration of anexample data frame 400 that may be transmitted or received by any one ofmodems 216. Data frame 400 includes a control or overhead field 402 anda payload field 404. Fields 402 and 404 include data bits used totransfer either control information (402) or payload data (404). Controlfield 402 includes control and header information used in managing acommunication link established between a respective one of modems 216and the remote station. Payload field 404 includes payload data (bits406), for example, data-to-be-transmitted between controller 214 and theremote station during a data call (that is, over the communication linkestablished between the modem and the remote station). For example, datareceived from controller 214, over data link 218 i, is packaged intopayload field 404.

[0072] Data frame 400 has a duration T, such as 20 milliseconds, forexample. The payload data in payload field 404 is conveyed at one of aplurality of data rates, including a maximum or full-rate (for example,9600 bits-per-second (bps)), a half-rate (for example, 4800 bps), aquarter-rate (for example, 2400 bps), or an eighth-rate (for example,1200 bps). Each of the modems 216 attempts to transmit data at thefull-rate (that is, at a maximum data rate). However, an over-limitmodem rate-limits, whereby the modem reduces its transmit data rate fromthe maximum rate to a lower rate, as will be discussed below. Also, eachof the modems 216 may transmit a data frame (for example, data frame400) without payload data. This is referred to as a zero-rate dataframe.

[0073] In one modem arrangement, each of the data bits 406 within aframe carries a constant amount of energy, regardless of the transmitdata rate. That is, within a frame, the energy-per-bit, E_(b), isconstant for all of the different data rates. In this modem arrangement,each data frame corresponds to an instantaneous modem transmit powerthat is proportional to the data rate at which the data frame istransmitted. Therefore, the lower the data rate, the lower the modemtransmit power. When transferring data at lower rates the energy of eachbit is generally spread out over time. That is, for half-rate the bitenergy is spread out over twice the length of time, quarter-rate, fourtimes the length of time, and so forth, By spreading the transmit energyacross a data frame in this manner, no energy spikes are caused duringportions of the frame which would exceed the allowed limit.

[0074] In addition, when transferring data at lower rates the energy ofeach bit is generally spread out over time. That is, for half-rate thebit energy is spread out over twice the length of time, quarter-rate,four times the length of time, and so forth, By spreading the transmitenergy across a data frame in this manner, no energy spikes are causedduring portions of the frame which would exceed the allowed limit.

[0075] Each of the modems 216 provides status reports to controller 214over respective data connections 218. FIG. 5 is an illustration of anexample status report 500. Status report 500 includes a modem data ratefield 502, a modem transmit power field 504, and an optional over-limit(also referred to as a rate-limiting) indicator field 506. Each modemreports the data rate of the last transmitted data frame in field 502,and the transmit power of the last transmitted data frame in field 504.In addition, each modem can optionally report whether it is in arate-limiting condition in field 506.

[0076] In another alternative modem arrangement, the modem can providestatus signals indicating the over-limit/rate-limiting condition, thetransmit power, and transmit data rate of the modem.

[0077] IV. Example Method

[0078]FIG. 6 is a flowchart of an example method or process 600representative of an operation of modem 300, and thus, of each of modems216. Method 600 assumes a data call has been established between a modem(for example, modem 216 a) and the remote station. That is, acommunication link including a forward link and a reverse link has beenestablished between the modem and the remote station.

[0079] At a first step 602, a transmit power limit P_(L) is establishedin the modem (for example, in modem 216 a).

[0080] At a next step 604, the modem receives a power control commandfrom the remote station over the forward link indicating a requestedtransmit power P_(R) at which the modem is to transmit data frames inthe reverse link direction. This command may be in the form of anincremental power increase or decrease command.

[0081] At a decision step 606, the modem determines whether any payloaddata has been received from controller 214, that is, whether or notthere is any payload data to transmit to the remote station. If not,processing proceeds to a next step 608. At step 608, the modem transmitsa data frame at the zero-rate, that is, without payload data. Thezero-rate data frame may include control/overhead information used tomaintain the communication link/data call, for example. The zero-ratedata frame corresponds to a minimum transmit power of the modem.

[0082] On the other hand, if there is payload data to transmit, thenmethod processing (control) proceeds from step 606 to a next step 610.At step 610, the modem determines whether or not it is not over-limit,that is, whether the modem is under-limit. In one arrangement,determining whether or not the modem is under-limit includes determiningwhether the requested transmit power P_(R) is less than the transmitpower limit P_(L). In this arrangement, the modem is consideredover-limit when the requested transmit power P_(R) is greater than orequal to P_(L). In an alternative arrangement, determining whether ornot the modem is under-limit includes determining whether an actualtransmit power P_(T) of the modem is less than the transmit power limitP_(L). In this arrangement, the modem is considered over-limit whenP_(T) is greater than or equal P_(L). The modem may use power monitor312 in determining whether its transmit power P_(T), for example, thetransmit power of signal 222 _(T), is less than the transmit power limitP_(L).

[0083] While the modem is not-over limit, the modem transmits a dataframe, including payload data and control information, at a maximum datarate (for example, the full-rate) and at a transmit power level P_(T)that is in accordance with the requested transmit power P_(R). In otherwords, the modem transmit power P_(T) tracks the requested transmitpower P_(R).

[0084] When P_(T) or P_(R) is equal to or greater than P_(L), the modemis over-limit, and thus rate-limits from a current rate (for example,the full-rate) to a lower transmit data rate (for example, to thehalf-rate, quarter-rate, eighth-rate or even the zero-rate), therebyreducing the transmit power P_(T) of the modem relative to when themodem was transmitting at the full-rate. Therefore, rate-limiting inresponse to either of the over-limit conditions described above is aform of modem self power-limiting, whereby the modem maintains itstransmit power P_(T) below the transmit power limit P_(L). Also, theover-limit/rate-limiting condition, as reported in status report 500,indicates to controller 214 that the requested power P_(R), or theactual transmit power P_(T) in the alternative arrangement, is greaterthan or equal to the transmit power limit P_(L). It should beappreciated that while the modem may be operating at the zero-rate inthe transmit (that is, reverse link) direction, because it either israte-limiting (for example, in step 610) or has no payload data totransmit (step 608), it may still receive full-rate data frames in thereceive (that is, forward link) direction.

[0085] Although it can be advantageous for the modem to self rate-limitin response to the over-limit condition, an alternative arrangement ofthe modem does not rate-limit in this manner. Instead, the modem reportsthe over-limit condition to controller 214, and then waits for thecontroller to impose rate-limiting adjustments. A preferred arrangementuses both approaches. That is, the modem self rate-limits in response tothe over-limit condition, and the modem reports the over-limit conditionto controller 214, and in response, the controller imposes rate-limitingadjustments on the modem.

[0086] After both step 608 and step 610, the modem generates a statusreport (for example, status report 500) at a step 612, and provides thereport to controller 214 over a respective one of data links 218.

[0087] V. Fixed Transmit Power Limit Embodiments

[0088]FIG. 7 is a flowchart of an example method performed by MWT 206,accordance with the present embodiments. Method 700 includes aninitializing step 702. Step 702 includes further steps 704, 706, and708. At step 704, controller 214 establishes an individual transmitpower limit P_(L) in each of modems 216. The transmit power limits arefixed over time in method 700.

[0089] At step 706, controller 214 establishes a data call over each ofmodems 216. In other words, a communication link, including both forwardand reverse links, is established between each of the modems 216 and theremote station. The communication links operate concurrently with oneanother. In an exemplary arrangement of the present invention, thecommunication links are CDMA based communication links.

[0090] In the embodiments, a modem may be designated as an active modemor as an inactive modem. Controller 214 can schedule active modems, butnot inactive modems, to transmit payload data. Controller 214 maintainsa list identifying currently active modems. At a step 708, controller214 initially designates all of the modems as being active, by addingeach of the modems to the active list, for example.

[0091] At a next step 710, assuming controller 214 has received datathat needs to be transmitted to the remote station, controller 214schedules each of the active modems to transmit payload data. In a firstpast through step 710, all of modems 216 are active (from step 708).However, in subsequent passes through step 710, some of modems 216 maybe inactive, as will be described below.

[0092] Controller 214 maintains a queue of data-to-be-transmitted foreach of the active modems, and supplies each data queue with datareceived from the external data sources over link 210. Controller 214provides data from each data queue to the respective active modem.Controller 214 executes data-loading algorithms to ensure the respectivedata queues are generally, relatively evenly loaded, so that each activemodem is concurrently provided with data-to-be-transmitted. Aftercontroller 214 provides data to each modem, each modem in turn attemptsto transmit the data in data frames at the full-rate and in accordancewith the respective requested transmit power P_(R), as described abovein connection with FIG. 6.

[0093] At step 710, controller 214 also de-schedules inactive modems bydiverting data-to-be-transmitted away from the inactive modems andtoward the active modems. However, there are no inactive modems in thefirst pass through step 710, since all of the modems are initiallyactive after step 708, as mentioned above.

[0094] At a next step 712, controller 214 monitors the modem statusreports from all of the inactive and active modems.

[0095] At a next step 714, controller 214 determines whether any of themodems 216 are over-limit, and thus rate-limiting, based on the modemstatus reports. If controller 214 determines that one or more (that is,at least one) of the modems are over-limit, then controller 214deactivates only these over-limit modems, at a step 716. For example,controller 214 can deactivate an over-limit modem by removing it fromthe active list.

[0096] If none of the modems are determined to be over-limit at step714, the method or processing proceeds to a step 718. Processing alsoproceeds to step 718 after any over-limit modems are deactivated in step716. At step 718, controller 214 determines whether or not any of themodems previously deactivated at step 716 need to be activated (that is,reactivated). Several techniques for determining whether modems shouldbe activated are discussed below. If the answer at step 718 is yes(modems need to be reactivated), then processing proceeds to a step 720,and controller 214 activates the previously deactivated modems that needto be activated, for example, by reinstating the modems on the activelist.

[0097] If none of the previously deactivated modems need to beactivated, then processing proceeds from step 718 back to step 710.Also, processing proceeds from step 720 to step 710. Steps 710 through720 are repeated over time, whereby over-limit ones of modems 216 aredeactivated at step 716 and then reactivated at step 718 as appropriate,and correspondingly de-scheduled and re-scheduled at step 710.

[0098] When an over-limit modem is deactivated at step 716 (that is,becomes inactive), and remains deactivated through step 718, the modemwill be descheduled in the next pass through step 710. In other words,controller 214 will no longer provide data to the deactivated modem.Instead, controller 214 will divert data to active modems. If it isassumed that the data call associated with the deactivated modem has notbeen torn-down (that is, terminated), then de-scheduling the modem atstep 710 will cause the deactivated modem to have no payload data totransmit, and will thus cause the modem to operate at the zero-rate andat a corresponding minimum transmit power level on the reverse link (seesteps 606 and 608, described above in connection with FIG. 6). Thiskeeps the data call alive or active on the deactivated/descheduledmodem, so the modem can still receive full-rate data frames on theforward link. When a data call associated with a modem is torn-down,that is, terminated or ended, the modem stops transmitting and receivingdata altogether.

[0099] Deactivating the over-limit modem at step 716 ultimately causesthe modem to reduce its transmit data rate and corresponding transmitpower in the reverse link direction. In this manner, controller 214individually controls the modem transmit power limits (and thus modemtransmit powers), and as a result, can maintain the aggregate transmitpower of signal 230 at a level below the aggregate transmit power limitof MWT 206.

[0100] Alternative arrangements of method 700 are possible. As describedabove, deactivating step 716 includes deactivating an over-limit modemby designating the modem as inactive, for example, by removing the modemfrom the active list. Conversely, activating step 720 includesreinstating the deactivated modem to the active list. In an alternativearrangement of method 700, deactivating step 716 further includestearing-down (that is, terminating) the data call (that is, thecommunication link) associated with the over-limit modem. Also in thisalternative arrangement, activating step 720 further includesestablishing another data call over the previously deactivated modem, sothat the modem can begin to transmit data to and receive data from theremote station.

[0101] In another alternative arrangement of method 700, deactivatingstep 716 further includes deactivating all of the modems, whetherover-limit or not over-limit, when any one of the over-limit modems isdetected at step 714. In this arrangement, deactivating the modems mayinclude designating all of the modems as inactive, and may furtherinclude tearing-down all of the data calls associated with the modems.

[0102]FIG. 8 is a flowchart expanding on transmit limit establishingstep 704 of method 700. At a first step 802, controller 214 derives thetransmit power limit for each of modems 216. For example, controller 214may calculate the transmit power limits, or simply access predeterminedlimits stored in a memory look-up table. At a next step 804, controller214 provides each of the modems 216 with a respective one of thetransmit power limits, and in response, the modems store theirrespective transmit power limits in their respective memories.

[0103]FIG. 9 is a flowchart expanding on determining step 718 of method700. Controller 214 monitors (at step 712, for example) the respectivereported transmit powers of the deactivated/inactive modems that aretransmitting at the zero-rate. At a step 902, controller 214 derives,from the reported modem transmit powers, respective extrapolated modemtransmit powers representative of when the modems transmit at themaximum transmit data rate.

[0104] At a next step 904, controller 214 determines whether eachextrapolated transmit power is less than the respective modem transmitpower limit P_(L). If yes, then processing proceeds to step 720 wherethe respective modem is activated, because it is likely the modem willnot exceed the power limit. If not, the modem remains deactivated, andflow of the method proceeds back to step 710.

[0105]FIG. 10 is a flowchart of another example method 1000 performed byMWT 206. Method 1000 includes many of the method steps describedpreviously in connection with FIG. 7, and such method steps will not bedescribed again. However, method 1000 includes a new step 1004 followingstep 716, and a corresponding determining step 1006. At step 1004,controller 214 initiates an activation timeout period (for example,using timer 217) corresponding to each modem deactivated at step 716.Alternatively, controller 214 can schedule a future activationtime/event corresponding to each modem deactivated in step 716.

[0106] At determining step 1006, controller 214 determines whether it istime to activate any of the previously deactivated modems. For example,controller 214 determines whether any of the activation timeout periodshave expired, thereby indicating it is time to activate thecorresponding deactivated modem. Alternatively, controller 214determines whether the activation time/event scheduled at step 1004 hasarrived.

[0107] Alternative arrangements of method 1000, similar to thealternative arrangements discussed above in connection with method 700,are also envisioned.

[0108] VI. Fixed Transmit Power Limit Arrangements

[0109] 1. Uniform Limits

[0110] In one fixed limit arrangement, a uniform set of fixed transmitpower limits is established across all of modems 216. That is, eachmodem has the same transmit power limit as each of the other modems.FIG. 11 is an example plot of Power versus Modem index(i) identifyingrespective ones of the modems 216, wherein uniform, modem transmit powerlimits P_(L1) are depicted. As depicted in FIG. 11, modem(1) correspondsto power limit P_(L1), modem(2) corresponds to power limit P_(L2), andso on.

[0111] In one arrangement of uniform limits, each transmit power limitP_(L) is equal to the aggregate transmit power limit APL divided by thetotal number N of modems 216. Under this arrangement of uniform limits,when all of the modems have respective transmit powers equal to theirrespective transmit power limits, the aggregate transmit power for allof the modems will just meet, and not exceed, the APL. An example APL inthe present invention is approximately 10 or 11 decibel-Watts (dBW).

[0112]FIG. 11 also represents an example transmit scenario for MWT 206.Depicted in FIG. 11 are representative, requested modem transmit powersP_(R1) and P_(R2) corresponding to modem(1) and modem(2). The exampletransmit scenario depicted in FIG. 11 corresponds to the scenario inwhich all of the requested modem transmit powers are below therespective, uniform transmit power limits. In this situation, none ofthe modems are over-limit, and thus rate-limiting.

[0113]FIG. 12 is another example transmit scenario similar to FIG. 11,except that modem(2) has a requested power P_(R2) exceeding respectivetransmit power limit P_(L2). Therefore, modem(2) is over-limit, and thusrate-limiting. Since modem(2) is over-limit, controller 214 deactivatesmodem(2) in accordance with method 700 or method 1000, thereby causingmodem(2) to transmit at a zero-data rate, and at a correspondinglyreduced transmit power level 1202.

[0114] 2. Tapered Limits

[0115]FIG. 13 is an illustration of an alternative, tapered arrangementfor the fixed modem transmit power limits. As depicted, the taperedarrangement includes progressively decreasing transmit power limitsP_(L1) in respective successive ones of the N modems, where i=1 . . . N.For example, transmit power limit P_(L1) for modem(1) is less thantransmit power limit P_(L2) for modem(2), which is less than transmitpower limit P_(L3), and so on down the line.

[0116] In one tapered arrangement, each of the transmit power limitsP_(Li) is equal to the APL divided by the total number of modems havingtransmit power limits greater than or equal to P_(L1) For example,transmit power limit P_(L5) is equal to the APL divided by five (5),which is the number of modems having transmit power limits greater thanor equal to P_(L5). In another tapered arrangement, each transmit powerlimit P_(Li) is equal to the transmit power limit mentioned above (thatis, the APL divided by the total number of modems having transmit powerlimits greater than or equal to P_(Li)) less a predetermined amount,such as one, two or even three decibels (dB). This permits a safetymargin in the event that the modems tend to transmit at an actualtransmit power level that is slightly higher than the respectivetransmit power limits, before they are deactivated.

[0117] Assume a transmit scenario where all of the modems transmit atapproximately the same power, and all of the transmit powers areincreasing over time. Under the tapered arrangement, modem(N)rate-limits first, modem(N−1) rate limits next, modem(N−2) rate-limitsthird, and so on. In response, controller 214 deactivates/deschedulesmodem(N) first, modem(N−1 second, modem(N−3) third, and so on.

[0118] VII. Modem Calibration—Determining Gain Factors g(i)

[0119] As described above in connection with FIG. 2, each modem 216 igenerates a transmit signal 222 i _(T) having a respective transmitpower level. Also, each modem 216 i generates a status report includinga modem transmit power estimate P_(Rep)(i) of the respective transmitpower level. Each modem transmit signal 222 i _(T) traverses arespective transmit path from modem 222 i to the output of transmitamplifier 228. The respective transmit path includes RF connections,such as cables and connectors, power combiner/splitter assembly 220, andtransmit amplifier 228. Therefore, transmit signal 222 i _(T)experiences a respective net power gain or loss g(i) along therespective transmit path. An example gain for the above-mentionedtransmit path is approximately 29 dB.

[0120] Accordingly, the gain or loss g(i) of the respective transmitpath may cause the power level of respective transmit signal 222 i _(T)at the output of modem 222 i to be different from the transmit powerlevel at the output of transmit amplifier 228. Therefore, the respectivemodem transmit power estimate P_(Rep)(i) may not accurately representthe respective transmit power at the output of transmit amplifier 228. Amore accurate estimate P_(O)(i) of the transmit power at the output oftransmit amplifier 228 (due to modem 222 i), is the reported powerP_(Rep)(i) adjusted by the corresponding gain/loss amount g(i).Therefore, g(i) is referred to as a modem dependent gain correctionfactor g(i), or the modem gain factor g(i) for modem 222 i.

[0121] When reported modem transmit power estimate P_(Rep)(i) and modemgain correction factor g(i) both represent power terms (as expressed indecibels or Watts, for example), the corrected transmit power estimateP_(O)(i) is given by:

P _(O)(i)=g(i)+P _(Rep)(i).

[0122] Alternatively, when reported transmit power estimate P_(Rep)(i)and modem gain correction factor g(i), in Watts, for example, thetransmit power P_(O)(i) is given by:

P _(O)(i)=g(i)P _(Rep)(i).

[0123] It is useful to be able to calibrate MWT 206 dynamically, todetermine the gain correction factors g(i) corresponding to all of the Nmodems. Once the factors g(i) are determined, they can be used tocalculate more accurate individual and aggregate modem transmit powerestimates from the modem transmit power reports.

[0124]FIG. 14 is a flowchart of an example method of calibrating modems216 in MWT 206. At a first step 1405, controller 214 schedules all Nmodems 216 to transmit data, so as to cause all of the modems totransmit data, concurrently.

[0125] At a next step 1410, controller 214 collects status reports 500,including respective reported transmit powers P_(Rep)(i), where irepresents modem i, and i=1= . . . N.

[0126] At a next step 1420, controller 214 receives an aggregatetransmit power measurement P_(Agg) for all of the N modems, for example,as determined by transmit power monitor 234.

[0127] At a next step 1425, controller 214 generates an equationrepresenting the aggregate transmit power as a cumulative function ofreported transmit powers P_(Rep)(i) and corresponding unknown, modemdependent gain correction factors g(i). For example, aggregate transmitpower P_(Agg) is represented as:$P_{Agg} = {\sum\limits_{i = 1}^{N_{N}}\quad {{g(i)}{{P_{Rep}(i)}.}}}$

[0128] At a next step 1430, previous steps 1405, 1410, 1420 and 1425 arerepeated N times to generate N simultaneous equations in P_(Rep)(i) andunknown gain correction factors g(i).

[0129] At a next step 1435, controller 214 determines the N gaincorrection factors g(i) by solving the N equations generated in step1430. Determined gain correction factors g(i) are stored in memory 215of MWT 206, and used as needed to adjust/correct modem transmit powerestimates P_(Rep)(i) in the methods of the invention, described below.Method 1400 may be scheduled to repeat periodically to update factorsg(i) over time.

[0130] VIII. Methods Using Dynamically Updated Transmit Limits

[0131] 1. Methods Using Energy-Per-Bit Determinations

[0132]FIG. 15 is a flowchart of an example method 1500 of operating MWT206, using dynamically updated individual modem transmit power limits.In method 1500, controller 214 initializes (step 702), schedules anddeschedules active and inactive ones of modems 216 (step 710), andmonitors status reports from the modems (step 712), as described above.At a next step 1502, controller 214 determines whether to modify (forexample, increase or decrease) or maintain the number of active modemsof MWT 206, in order to maximize an aggregate reverse link data rate(that is, the aggregate transmit data rate) without exceeding theaggregate transmit power limit of the MWT.

[0133] At a next step 1504, controller 214 increases, decreases, ormaintains the number of active modems, as necessary, in accordance withstep 1502. To increase the number of active modems, controller 214 addsone or more previously inactive modems to the active list. Conversely,to decrease the number of active modems, controller 214 deletes one ormore previously active modems from the active list.

[0134] At a next step 1506, controller 214 updates/adjusts individualtransmit power limits in at least some of modems 216, as necessary.Techniques for adjusting individual transmit power limits will bedescribed further below. In step 1506, the individual transmit powerlimits are adjusted across modems 216 such that when all of theindividual transmit limits are combined together into a combinedtransmit power limit, the combined transmit power limit does not exceedthe aggregate transmit power limit of MWT 206. Exemplary transmit powerlimit arrangements that may be used with method 1500 are described laterin connection with Table 1 and FIG. 19. A reason for varying modemtransmit power limits in method 1500 is to avoid rate-limitingconditions in the modems. Also, a reason for deactivating modems (thatis, decreasing the number of active modems) includes avoidingrate-limiting conditions so as to increase the overall transmit datarate on the reverse-link while operating under the aggregate transmitpower limit.

[0135] At first blush, it might appear that deactivating modems woulddecrease, not increase, the transmit data rate. However, operating anumber of modems, for example, 16 modems, at their rate-limited datarates (for example, at 4800 bps) achieves a lower effective data ratethan operating a lesser number modems, for example 8 modems, at theirfull rates (for example, 9600 bps), even though each case may have thesame aggregate transmit power. This is because the ratio of overheadinformation (used to manage the data calls, for example) toactual/useful data (used by end users, for example) is disadvantageouslygreater for rate limiting modems compared to non-rate limiting modems.

[0136]FIG. 16 is a flowchart of an example method 1600 expanding onmethod 1500. Method 1600 includes a step 1602 expanding on step 1502 ofmethod 1500. Step 1602 includes further steps 1604 and 1606. At step1604, controller 214 determines a maximum number N_(Max) of activemodems that can concurrently transmit at their respective maximum datarates (for example, at 9600 bps), without exceeding the aggregatetransmit power limit of MWT 206. It is assumed that N_(Max) is less thanor equal to a total number N of modems 216.

[0137] At next step 1606, controller 214 compares the maximum numberN_(Max) to a number M of previously active modems (that is, the numberof active modems used in a previous pass through step 710, describedabove).

[0138] A next step 1610, corresponding to step 1504 of method 1500,includes further steps 1612, 1614 and 1616. If the maximum numberN_(Max) of active modems from step 1604 is greater than the number M ofpreviously active modems, the method flow proceeds from step 1606 tonext step 1612. At step 1612, controller 214 increases the number M ofactive modems to the maximum number N_(Max) of active modems. To dothis, controller 214 selects an inactive modem to activate from amongthe N modems.

[0139] Alternatively, if the maximum number N_(Max) of modems is lessthan M, then processing proceeds from step 1606 to step 1614. At step1614, controller 214 decreases the number of active modems. To do this,controller 214 selects an active modem to deactivate. Steps 1612 and1614 together represent an adjusting step (also referred to as amodifying step) where the number M of previously active modems ismodified in preparation for a next pass through steps 710, 712, and soon.

[0140] Alternatively, if the maximum number N_(Max) is equal to M, thenprocessing proceeds from step 1606 to step 1616. In step 1616,controller 214 simply maintains the number of active modems at M, forthe next pass through steps 710, 712, and so on.

[0141] Processing proceeds from both modifying steps 1612 and 1614 to anext, limit adjusting step 1620. At step 1620, controller 214 increasesthe individual transmit power limits in the one or more modems that wereactivated at step 1612. Conversely, controller 214 decreases theindividual power limits in the one or more modems that were deactivatedin step 1614.

[0142] The method proceeds from steps 1610 and 1620 back toscheduling/descheduling step 710, and the process described aboverepeats.

[0143]FIG. 17 is a flowchart of an example method 1700 of determiningthe maximum number N_(Max) of active modems using an averageenergy-per-transmitted-bit of the N modems. Method 1700 expands on step1604 of method 1600. At a first step 1702, controller 214 determines anaggregate transmit data rate based on the respective transmit data ratesreported by the N modems. For example, controller 214 adds together allof the transmit data rates reported by the N modems in respective statusreports 500.

[0144] At a next step 1704, controller 214 determines an aggregate powerlevel of transmit signal 230, at the output of transmit amplifier 228.For example, controller 214 may receive transmit power measurements(signal 236) from transmit power monitor 234. Alternatively, controller214 may aggregate individual modem transmit power estimates P_(Rep)(i)(as corrected using factors g(i)) received from the individual modems inrespective status reports 500.

[0145] At a next step 1706, controller 214 determines the averageenergy-per-transmitted-bit across the N modems 216 based on theaggregate data rate and the aggregate transmit power. In one arrangementof the embodiments, controller 214 determines the averageenergy-per-transmitted-bit in accordance the following relationships:

BE _(b) _(—) _(avg) =P(t)Δt=E _(T), and, therefore,

E _(b) _(—) _(avg)=(P(t)Δt)/B=E _(T) /B,

[0146] where:

[0147] Δt is a predetermined measurement time interval (for example, theduration of a transmitted frame, such as 20 ms),

[0148] B is the aggregate data rate during time interval Δt,

[0149] E_(b) _(—) avg is the average energy-per-transmitted-bit duringtime interval Δt,

[0150] P(t) is the aggregate transmit power during time interval Δt, and

[0151] E_(T) is the total energy of all the bits transmitted during timeinterval Δt.

[0152] At a next step 1708, controller 214 determines the maximum numberN_(Max) based on the average energy-per-transmitted-bit and theaggregate transmit power limit. In one arrangement, controller 214determines the maximum number N_(Max) in accordance with the followingrelationships:

((R _(max) N _(Max) +R _(min)(N−N _(Max)))E _(b) _(—) _(avg) =APL, andtherefore

N _(Max)=((APL/E _(b) _(—) _(avg))−P _(min) N)/(R _(max) −R _(min)),

[0153] where:

[0154] APL is the aggregate transmit power limit of MWT 206 (forexample, 10 or 11 decibel-Watts (dBW)),

[0155] Rmax is a maximum data rate of the N modems (for example, 9600bps),

[0156] Rmin is a minimum data rate of the N modems (for example, 2400bps),

[0157] E_(b) _(—) avg is the average energy-per-transmitted-bit duringtime interval Δt,

[0158] N is the total number of modems 216, and

[0159] N_(Max) is the maximum number of active modems to be determined.

[0160]FIG. 18 is a flowchart of an example method 1800 of determiningthe maximum number N_(Max) of active modems, using an individualenergy-per-transmitted-bit for each of modems 216. Method 1800 expandson step 1604 of method 1600. At a first step 1802, controller 214determines an individual energy-per-transmitted-bit E_(b)(i) for eachmodem using modem reports 500. In one arrangement of the embodiment,controller 214 determines each energy-per-transmitted-bit E_(b)(i) inaccordance the following relationship:

E _(b)(i)=g(i)P _(Rep)(i)Δt/Bi,

[0161] where:

[0162] Δt is a predetermined measurement time interval,

[0163] E_(b)(i) is the individual energy-per-transmitted-bit for modemi, where i=1 . . . N, over time interval Δt,

[0164] P_(Rep)(i) is a reported modem transmit power (that is, atransmit power estimate for modem i), and

[0165] g(i) is a modem dependent gain correction factor, also referredto as a gain calibration factor (described above in connection with FIG.14), and

[0166] Bi is the transmit data rate of modem i.

[0167] At a step 1804, controller 214 sorts the modems according totheir respective energy-per-transmitted-bits E_(b)(i).

[0168] At a next step 1805, controller 214 determines the maximum numberN_(Max) of active modems based on the individual modemenergy-per-transmitted-bits, using an iterative process. In oneembodiment, the iterative process of step 1805 determines the maximumnumber N_(Max) of active modems that can be supported, using thefollowing equation:${{APL} = {{\sum\limits_{i = 1}^{N_{Max}}\quad {P_{\max}{E_{b}(i)}}} + {\sum\limits_{i = N_{Max}}^{N}\quad {P_{\min}{E_{b}(i)}}}}},$

[0169] where:

[0170] APL is the aggregate transmit power limit,

[0171] P_(max) is the maximum data rate for each modem,

[0172] P_(min) is the minimum data rate for each modem, and

[0173] E_(b)(i) is the individual energy-per-transmitted-bit for modemi.

[0174] Step 1805 is now described in further detail. A step 1806 withinstep 1805 is an initializing step in the iterative process, whereinmodem 214 sets a test number N_(Act) of active modems equal to one (1).Test number N_(Act) represents a test, maximum number of active modems.At a next step 1808, modem 214 determines an expected transmit powerP_(Exp) using the test number N_(Act) of modems. In step 1808, it isassumed that the test number N_(Act) of modems having the lowestindividual energy-per-transmitted-bits among the N modems each transmitat a maximum data rate (for example, 9600 bps). In the embodimentmentioned above, step 1808 determines the expected transmit power inaccordance with the following equation:${P_{E\quad {xp}} = {{\sum\limits_{i = 1}^{N_{act}}\quad {P_{\max}{E_{b}(i)}}} + {\sum\limits_{i = N_{act}}^{N}\quad {P_{\min}{E_{b}(i)}}}}},$

[0175] At a next step 1809, controller 214 compares the expectedtransmit power P_(Exp) to the APL. If P_(Exp)<APL, then more activemodems can be supported. Thus, the test number N_(Act) of active modemsis incremented (step 1810), and the method proceeds back to step 1808.

[0176] Alternatively, if P_(Exp)=APL, then the maximum number N_(Max) ofactive modems is set equal to the present test number N_(Act) (step1812).

[0177] Alternatively, if P_(Exp)>APL, then the maximum number N_(Max) isset equal to the previous test number of active modems, that is,N_(Act)−1 (step 1814).

[0178] If P_(Exp) is neither equal to nor greater than APL then theprocess returns to step 1810 and step 1809. At some point a maximumnumber of modems may be reached or exceeded and either step 1812 or1814, respectively, are reached. The process for recalculating APLchecking the current N (number of access terminals in use), or checkingP_(Exp) relative to APL, may be repeated every so often or on a periodicbasis as part of an iterative procedure to prevent overdriving the poweramplifier.

[0179] IX. Example Transmit Power Limits

[0180] Table 1, below, includes exemplary modem transmit power limitsthat may be used in the present invention. TABLE 1 A B C D No. activeActive Modem Active Modem Active Modem modems Limits (dBm) Limits (dBm)Limits (dBm) (Total N = 16) APL = 10 dBW APL = 11 dBW APL = 10 dBW 1.05.0 5.2 4.2 2.0 5.0 4.6 3.6 3.0 5.0 4.0 3.0 4.0 5.0 3.5 2.5 5.0 4.0 3.12.1 6.0 3.2 2.7 1.7 7.0 2.5 2.3 1.3 8.0 2.0 2.0 1.0 9.0 1.5 1.7 0.7 10.01.0 1.4 0.4 11.0 0.6 1.1 0.1 12.0 0.2 0.9 −0.1 13.0 −0.1 0.6 −0.4 14.0−0.5 0.4 −0.6 15.0 −0.8 0.2 −0.8 16.0 −1.0 0.0 −1.0

[0181] The transmit power limits of Table 1 may be stored in memory 215of MWT 206. Table 1 assumes MWT 206 includes a total of N=16 modems.Each row of table 1 represents a corresponding number (such as 1, 2, 3,and so on, down the rows) of active ones of the N modems, at any giventime. Each row of Column A identifies a given number of active modems.The number of inactive modems corresponding to any given row of Table 1is the difference between the total number of modems (16) and the numberof active modems specified in the given row.

[0182] Columns B, C and D collectively represent three differentindividual transmit power limit arrangements of the present invention.The transmit limit arrangement of column B assumes an APL of 10 dBW inMWT 206. Also, the arrangement of column B assumes that, in any givenrow, all of the active modems receive a common maximum transmit limit,while all of the inactive modems receive a common minimum transmit limitequal to zero. For example in column B, when the number of active modemsis six (6), a common maximum transmit limit of 3.2 decibel-milliwatt(dBm) is established in each of the active modems, and a common minimumtransmit limit of zero is established in each of the ten (10) inactivemodems. The sum of the maximum transmit power limits in all of theactive modems corresponding to any given row is equal to the APL.

[0183] The transmit limit arrangement of column C assumes an APL of 11dBW in MWT 206. Also, the arrangement of column C assumes that, for anygiven number of active modems (that is, for each row in Table 1), all ofthe active modems receive a common maximum transmit limit, while all ofthe inactive modems receive a common minimum transmit limit equal to themaximum transmit limit less six (6) dB. For example in column C, whenthe number of active modems is six (6), a maximum transmit limit of 2.7dBm is established in each of the six (6) active modems, and a minimumtransmit limit of (2.7-6) dBm is established in each of the ten (10)inactive modems. The sum of the maximum transmit power limits in all ofthe active modems, together with the sum of the minimum transmit powerlimits in all of the inactive modems, corresponding to any given row isequal to the APL. Since the transmit power limit in each of the inactivemodems is greater than zero, the inactive modems may be able to transmitat respective minimum data rates, or at least at the zero-data rate, inorder to maintain their respective data links active.

[0184] The transmit limit arrangement of column D is similar to that ofcolumn C, except a lower APL of 10 dBW is assumed in the arrangement ofcolumn D. The arrangement of column D assumes that, for any given numberof active modems (that is, for each row in Table 1), all of the activemodems receive a common maximum transmit limit, while all of theinactive modems receive a common minimal transmit limit equal to themaximum transmit limit less six (6) dB. For example, from column D, whenthe number of active modems is six (6), a maximum transmit limit of 1.7dBm is established in each of the active modems, and a transmit limit of(1.7-6) dBm is established in each of the ten (10) inactive modems.

[0185] Controller 214 can use the limits specified in Table 1 toestablish and adjust individual transmit limits in modems 216 in methods1500 and 1600, described above in connection with FIGS. 15 and 16. Forexample, assume the transmit limit arrangement of Table 1, column D, isbeing used with method 1600. Assume the number of active modems in aprevious pass through step 710 is seven. During the previous pass, atransmit limit of 1.3 dBm is established in each of the seven activemodems, and a transmit limit of (1.3-6) dBm is established in the nineinactive modems (see the entry in column D corresponding to seven activemodems). Also assume that in the next pass through steps 1602 and 1614,the number of active modems is decreased from seven down to six. Then,at limit adjusting step 1620, a new transmit limit of 1.7 dB isestablished in each of the six active modems, and a transmit limit of(1.7-6) dB is established in each of the ten remaining inactive modems.

[0186]FIG. 19 is a graphical representation of the information presentedin Table 1. FIG. 19 is a plot of transmit limit power (in dBm) versusthe number of active modems (labeled as N) for each of the transmitlimit arrangements listed in columns B, C and D of Table 1. In FIG. 19,the transmit limit arrangement of column B is represented by a curve COLB, the limit arrangement of column C is represented by a curve COL C,and the limit arrangement of column D is represents by a curve COL D.

[0187] X. Method of Adjusting Modem Transmit Limits to Track ModemTransmit Powers

[0188]FIG. 20 is a flowchart of an example method 2000 of operating MWT206 using dynamically varying individual modem transmit power limits.Method 2000 causes each individual modem transmit power limit to trackthe transmit power of the modem associated with the transmit powerlimit. Method 2000 includes steps 702, 710, and 712, as describedpreviously. Steps 710 and 712 are repeated until controller 214 detectsan over-limit (OL) modem at a step 2002, based on status reports 500from the modems. When controller 214 detects an over-limit modem at step2002, the controller determines whether or not to adjust or maintain thepresent number of active modems at a step 2004. In this manner, method2000 is reactive to over-limit conditions in the modems of MWT 206. Thisprocessing allows one to increase the number of modems when the channelis good and extra throughput is required.

[0189] Step 2004 corresponds to step 1502 of method 1500, mentionedabove in connection with FIG. 15. Step 2004 includes steps 2006, 2008,and 2010. At step 2006, controller 214 determines the aggregate transmitpower of the N modems 216. For example, controller 214 may receive atransmit power measurement from transmit power monitor 234.Alternatively, controller 214 may: receive reported transmit powerestimates P_(Rep)(i) from the N modems; derive corrected power estimatesP_(O)(i) from the reported estimates using gain correction factors g(i);and then combine the corrected power estimates into an aggregatetransmit power estimate, representing the aggregate transmit power ofthe N modems. Gain correction factors g(i) and corrected estimatesP_(O)(i) are described above in connection with FIG. 14.

[0190] At a next step 2008, controller 214 determines whether or not anaggregate transmit power margin (ATM) of MWT 206 is sufficient to permitan increase in the transmit power limit of the over-limit modem. The ATMrepresents the total amount of transmit power headroom existing betweenthe aggregate transmit power and the aggregate transmit power limit. Inone arrangement, the ATM is defined as a difference between theaggregate transmit power of the N modems and the aggregate transmitpower limit.

[0191] Step 2008 can include a simple comparison to determine whetherthe aggregate transmit power is less than the APL by a predeterminedamount required for increasing the individual transmit limit in theover-limit modem. An aggregate transmit power margin ATM of between 1 dBand 6 dB may be considered sufficient for increasing the transmit limitin the over-limit modem.

[0192] If the aggregate transmit margin ATM is insufficient to permit anincrease in the transmit limit of the over-limit modem, then controller214 takes further steps in an attempt to free-up or generate moreaggregate transmit margin so that the transmit limit in the over-limitmodem can be increased, and method processing proceeds to a next step2014. Step 2014 includes steps 2016 and 2018 for decreasing the numberof active modems. At step 2016, controller 214 sorts modems 216according to their respective transmit powers. For example, controller214 sorts the modems based on the respective reported transmit powerestimates P_(Rep)(i), as corrected by respective gain factors g(i).

[0193] At next step 2018, controller 214 deactivates a modem having thegreatest transmit power among the active modems. The eventual result ofdeactivating the modem in step 2018 is to reduce the aggregate transmitpower of the N modems, and thus correspondingly increase the aggregatetransmit margin ATM. Processing then proceeds to a transmit limitadjusting step 2020.

[0194] Returning again to step 2008, if the aggregate transmit marginATM is sufficient to increase the transmit limit in the over-limitmodem, then processing proceeds to step 2010. At step 2010, controller214 determines whether or not the aggregate transmit margin issufficient to increase the transmit limits in both the over-limit modemand another inactive modem. In other words, step 2010 determines whetherthere is sufficient transmit margin (for example, at least 3 dB oftransmit margin) to increase the number of active modems. If not (thatis, there is insufficient aggregate transmit margin to increase thenumber of active modems), then processing proceeds to a step 2022,wherein the number of active modems is maintained. The method proceedsfrom step 2022 to transmit limit adjusting step 2020.

[0195] On the other hand, if the aggregate transmit margin ATM issufficient to increase the number of active modems or increase thetransmit limit in the over-limit modem, then processing proceeds fromstep 2010 to a next step 2024, wherein the number of active modems isincreased or power increased to an active modem. That is, if there issufficient transmit margin then one is free to chose to apply this extrapower to any modem desired, regardless of whether one is over limit ornot. Processing proceeds from step 2024 to limit adjusting step 2020.Steps 2014, 2022 and 2024 of method 2000 correspond to adjusting step1504 of method 1500, while step 2020 corresponds to step 1506 of method1500.

[0196] At limit adjusting step 2020, controller 214 adjusts theindividual transmit power limits in at least some of the N modems basedon the aggregate transmit power limit, the aggregate transmit powermargin ATM, and the respective power estimates from the N modems,thereby causing each individual power limit to track the correspondingindividual modem transmit power. Flow proceeds from step 2020 back tostep 710.

[0197]FIG. 21 is a flow chart of an example method 2100 expanding onlimit adjusting step 2020 of method 2000. Processing proceeds from modemdeactivating step 2018 of method 2000 (from FIG. 20) to a step 2105 ofmethod 2100. At step 2105, controller 214 reduces the individualtransmit power limit in the modem deactivated in step 2018. Controller214 may reduce the individual transmit limit by 6 dB, for example. Thispermits a corresponding increase in the transmit power limit of theover-limit modem (determined in step 2002 of method 2000), withoutaltering a combined transmit power limit of all of the N modems. Thecombined transmit power limit of all of the N modems is the sum of the Nindividual transmit power limits. The combined transmit power limitshould not exceed the aggregate transmit power limit.

[0198] The method proceeds from modem activating step 2024 of method2000 (from FIG. 20) to a step 2110 of method 2100. At step 2110,controller 214 increases the individual transmit limit in the modemactivated in step 2024. Controller 214 may increase the individualtransmit limit in the activated modem by an amount equal to the transmitpower margin, less at least a few dB needed to increase the transmitlimit in the over-limit modem.

[0199] Processing proceeds from steps 2105 and 2110, and frommaintaining step 2022 of method 2000 (from FIG. 20), to a step 2115 ofmethod 2100. At step 2115, controller 214 adjusts the individualtransmit power limits in at least some of the N modems based on theaggregate transmit power limit and the respective transmit powerestimates from the N modems, to cause each individual transmit powerlimit to track its corresponding modem transmit power. The transmitpower limits are adjusted so that when all of the individual transmitpower limits are combined into a combined transmit power limit, thecombined transmit power limit is less than or equal to the aggregatetransmit power limit. Also, each individual transmit power limit ispreferably greater than the corresponding individual modem transmitpower, to avoid over-limit conditions in the modems. To achieve theresults mentioned above, controller 214 apportions the aggregatetransmit margin ATM across the N modems as necessary, and increases thetransmit limit in the over-limit modem.

[0200]FIG. 22 is a flow chart of an example method 2200 expanding onstep 2115. At a first step 2205, controller 214 determines the aggregatetransmit margin ATM. This step may be optional because the aggregatetransmit margin ATM may also be determined previously at step 2006.

[0201] At a next step 2210, controller 214 divides the aggregatetransmit margin among at least some of the N modems to derive theindividual transmit limits. In one arrangement, the aggregate transmitmargin is evenly divided among the N modems. For example, assume theaggregate transmit margin is divided into N equal portions, where eachportion is equal to X dB. Then the individual transmit limit for eachmodem 222 i may be derived by adding X dB to the estimated transmitpower P_(Rep)(i) of the modem. This produces a transmit limit in modem222 i that exceeds the estimated transmit power by X dB, and thus,likely avoids an over-limit condition in the modem. Also, as thisprocess is repeated over time, each individual transmit power limittracks the transmit power of the corresponding modem. That is, eachtransmit power limit tends to increase and decrease with thecorresponding modem transmit power.

[0202]FIG. 23A is an example plot of power versus modem index (i)identifying respective ones of modems 216 being controlled in accordancewith method 2000. FIG. 23A corresponds to an example transmit scenarioin MWT 206 occurring at a first time t₁. Modem(1) has a respective modemtransmit power P₁ and a respective transmit power limit P_(L1), modem(2)has a respective modem transmit power P₂ and a respective transmit powerlimit P_(L2), and so on. The depicted transmit powers P₁ can representactual modems transmit powers, reported modem transmit powersP_(Rep)(i), or adjusted modem transmit powers P_(O)(i). As depicted, therespective modem transmit power limits vary from modem to modem inaccordance with the respective modem transmit powers. Each modemtransmit power limit P_(Li) is slightly greater than the correspondingmodem transmit power P_(i).

[0203]FIG. 23B corresponds to an example transmit scenario in MWT 206occurring at a second time t₂, some time after first time t₁. Therespective modem transmit powers depicted in FIG. 23B have changed withrespect to FIG. 23A, however, the respective transmit power limits havealso changed in correspondence with the transmit powers. The powerlimits track the changes.

[0204]FIG. 23C corresponds to an example transmit scenario in MWT 206wherein the transmit power P₂ of modem(2) exceeds the transmit powerlimit. This corresponds to a possible over-limit condition of modem(2).In response, method 2000 increases the transmit power limit in modem(2)to avoid the over-limit condition, and redistributes any remainingaggregate transmit power margin among the other modems.

[0205]FIG. 23D corresponds to an example transmit scenario in MWT 206after method 2000 has reacted to the over-limit scenario of FIG. 23C. InFIG. 23D, transmit power limit P_(L2) of modem(2) has been adjusted bymethod 2000 to exceed transmit power P₂ of modem(2). Also, the decreasein modem transmit power P₃ provides a corresponding increase in theaggregate transmit power margin ATM. The increased ATM is allocatedacross the modems.

[0206] XI. MWT Computer Controller

[0207]FIG. 24 is a functional block diagram of an example controller(which can also be a plurality of controllers) 2400 representingcontroller 214. Controller 2400 includes a series of controller modulesfor performing the various method steps of the embodiments discussedabove.

[0208] A scheduler/de-scheduler 2402 schedules active modems to transmitpayload data, and to deschedule inactive modems, while a call manager2404 establishes data calls and tears-down data calls over the pluralityof modems 216.

[0209] A status monitor 2406 monitors status reports from modems 216,for example, to determine when various ones of the modems areover-limit, and collects modem transmit data rates and transmit powers.Status monitor 2406 may also determine an aggregate data rate and anaggregate transmit power based on the modem reports.

[0210] A deactivator/activator module 2408 acts to deactivate over-limitones (in the fixed limit arrangement of the present invention) of themodems (for example by removing the modems from the active list) and toactivate deactivated ones of the modems by reinstating the modems on theactive list. Module 2408 also activates/deactivates selected ones of themodems in accordance with steps 1504, 1612, 1614, 2014, and 2024 ofmethods 1500, 1600, and 2000.

[0211] A limit calculator 2410 operates to calculate/derive transmitpower limits for each of the modems 216. Limit calculator also accessespredetermined transmit power limits stored in memory 215, for example.Limit calculator 2410 calculates transmit power limits in accordancewith steps 1506, 1620, and 2020.

[0212] An initializer 2412 is used to supervise/manage initialization ofthe system, such as establishing initial transmit power limits in eachmodem, setting up calls over each modem, initializing various lists andqueues in MWT 206, and so on; a modem interface 2414 receives data fromand transmits data to modems 216; and a network interface 2416 operatesto receive and transmit data over interface 210.

[0213] A module 2420 is used for determining whether to adjust thenumber of active modems in accordance with steps 1502, 1602, and 2004 ofmethods 1500, 1600 and 2400. Module 2420 includes a sub-module 2422 fordetermining a maximum number of active modems that can be supportedbased on either an average-energy-per-transmitted-bit or individualmodem energy-per-transmitted-bits. Sub-module 2422 includes comparinglogic (such as a comparator) configured to operate in accordance withcomparing step 1606 of method 1600. Module 2420 also includessub-modules 2424 and 2426 for determining theaverage-energy-per-transmitted-bit and the individual modemenergy-per-transmitted-bits, respectively. Sub-modules 2424 and 2426, oralternatively, status monitor 2406, also determine an aggregate datarate and an aggregate transmit power based on modem reports. Module 2420also includes a sub-module 2428 for determining the sufficiency of anaggregate transmit power margin ATM in accordance with steps 2008 and2010 of method 2000.

[0214] A calibration module 2440 controls calibration in MWT 206 inaccordance with method 1400, for example. The calibration moduleincludes an equation generator to generate simultaneous equations and anequation solver to solve the equations to determine modem correctionfactors g(i). The calibration module can also call/incorporate othermodules, as necessary, to perform calibration of MWT 206.

[0215] A software interface 2450 is used for interconnecting all of theabove mentioned modules to one another.

[0216] Features of the present invention can be performed and/orcontrolled by processor/controller 214, which in effect comprises aprogrammable or software controllable element, device, or computersystem. Such a computer system includes, for example, one or moreprocessors that are connected to a communication bus. Althoughtelecommunication-specific hardware can be used to implement the presentinvention, the following description of a general purpose type computersystem is provided for completeness.

[0217] The computer system can also include a main memory, preferably arandom access memory (RAM), and can also include a secondary memoryand/or other memory. The secondary memory can include, for example, ahard disk drive and/or a removable storage drive. The removable storagedrive reads from and/or writes to a removable storage unit in a wellknown manner. The removable storage unit, represents a floppy disk,magnetic tape, optical disk, and the like, which is read by and writtento by the removable storage drive. The removable storage unit includes acomputer usable storage medium having stored therein computer softwareand/or data.

[0218] The secondary memory can include other similar means for allowingcomputer programs or other instructions to be loaded into the computersystem. Such means can include, for example, a removable storage unitand an interface. Examples of such can include a program cartridge andcartridge interface (such as that found in video game devices), aremovable memory chip (such as an EPROM, or PROM) and associated socket,and other removable storage units and interfaces which allow softwareand data to be transferred from the removable storage unit to thecomputer system.

[0219] The computer system can also include a communications interface.The communications interface allows software and data to be transferredbetween the computer system and external devices. Software and datatransferred via the communications interface are in the form of signalsthat can be electronic, electromagnetic, optical or other signalscapable of being received by the communications interface. As depictedin FIG. 2, processor 214 is in communications with memory 215 forstoring information. Processor 214, together with the other componentsof MWT 206 discussed in connection with FIG. 2, performs the methods ofthe present invention.

[0220] In this document, the terms “computer program medium” and“computer usable medium” are used to generally refer to media such as aremovable storage device, a removable memory chip (such as an EPROM, orPROM) within MWT 206, and signals. Computer program products are meansfor providing software to the computer system.

[0221] Computer programs (also called computer control logic) are storedin the main memory and/or secondary memory. Computer programs can alsobe received via the communications interface. Such computer programs,when executed, enable the computer system to perform certain features ofthe present invention as discussed herein. For example, features of theflow charts depicted in FIGS. 7-10, 14-18, and 20-22, can be implementedin such computer programs. In particular, the computer programs, whenexecuted, enable processor 214 to perform and/or cause the performanceof features of the present invention. Accordingly, such computerprograms represent controllers of the computer system of MWT 206, andthus, controllers of the MWT.

[0222] Where embodiments are implemented using software, the softwarecan be stored in a computer program product and loaded into the computersystem using the removable storage drive, the memory chips or thecommunications interface. The control logic (software), when executed byprocessor 214, causes processor 214 to perform certain functions of theinvention as described herein.

[0223] Features of the invention may also or alternatively beimplemented primarily in hardware using, for example, asoftware-controlled processor or controller programmed to perform thefunctions described herein, a variety of programmable electronicdevices, or computers, a microprocessor, one or more digital signalprocessors (DSP), dedicated function circuit modules, and hardwarecomponents such as application specific integrated circuits (ASICs) orprogrammable gate arrays (PGAs). Implementation of the hardware statemachine so as to perform the functions described herein will be apparentto persons skilled in the relevant art(s).

[0224] The previous description of the preferred embodiments is providedto enable a person skilled in the art to make or use the presentinvention. While the invention has been particularly shown and describedwith reference to embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention.

XII. CONCLUSION

[0225] The present invention has been described above with the aid offunctional building blocks illustrating the performance of specifiedfunctions and relationships thereof. The boundaries of these functionalbuilding blocks have been arbitrarily defined herein for the convenienceof the description. Alternate boundaries can be defined so long as thespecified functions and relationships thereof are appropriatelyperformed. Any such alternate boundaries are thus within the scope andspirit of the claimed invention. One skilled in the art will recognizethat these functional building blocks can be implemented by discretecomponents, application specific integrated circuits, processorsexecuting appropriate software and the like or many combinationsthereof. Thus, the breadth and scope of the present invention should notbe limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

What we claim as our invention is:
 1. A method of controlling transmitpower in a data terminal constrained to operate within an aggregatetransmit power limit, the data terminal including N wireless modemshaving their respective transmit outputs combined to produce anaggregate transmit output, the method comprising: (a) establishing anindividual transmit power limit in each of the N modems; (b) schedulingeach of a plurality of the N modems to transmit respective data; (c)receiving a respective, reported transmit power estimate from each ofthe N modems; and (d) adjusting the individual transmit power limits inat least some of the N modems based on the aggregate transmit powerlimit and the respective transmit power estimates from the N modems, tocause each individual transmit power limit to track a correspondingindividual modem transmit power.
 2. The method of claim 1, wherein step(d) comprises adjusting the individual transmit power limits such thatwhen the N individual transmit power limits are combined into a combinedtransmit power limit, the combined transmit power limit is less than orequal to the aggregate transmit power limit, and each individualtransmit power limit is greater than the corresponding individual modemtransmit power.
 3. The method of claim 2, further comprising: (f)periodically repeating steps (b), (c) and (d) to cause the individualtransmit power limits to track changes in the corresponding modemtransmit powers over time.
 4. The method of claim 1, further comprising,prior to step (a), establishing an individual wireless communicationlink between each of the N modems and a remote station, eachcommunication link including a forward link and a reverse link.
 5. Themethod of claim 4, wherein each wireless communication link is a CodeDivision Multiple Access (CDMA) communication link.
 6. The method ofclaim 1, wherein step (d) comprises: (d)(i) deriving new individualtransmit power limits for the N modems; and (d)(ii) updating the atleast some of the N modems with corresponding ones of the new individualtransmit power limits.
 7. The method of claim 1, wherein step (d)comprises: (d)(i) determining an aggregate transmit power for all of theN modems; (d)(ii) determining an aggregate transmit power margin basedon a difference between the aggregate transmit power and the aggregatetransmit power limit; and (d)(iii) dividing the aggregate transmit powermargin among the N modems to produce for each of the N modems anindividual transmit power limit that is greater than a correspondingmodem transmit power.
 8. The method of claim 7, wherein step (d) furthercomprises: producing a corrected transmit power estimate from eachtransmit power estimate using a corresponding predetermined, modem gaincorrection factor; wherein step (d)(i) comprises determining theaggregate transmit power using the corrected transmit power estimates;and wherein step (d)(iii) comprises using the corrected transmit powerestimates to represent the corresponding modem transmit powers.
 9. Themethod of claim 1, further comprising: prior to step (d), determining anover-limit one of the N modems; and wherein step (d) comprisesincreasing the transmit power limit of the over-limit modem.
 10. Themethod of claim 9, wherein: step (b) comprises scheduling active ones ofthe N modems to transmit their respective data; and step (d) comprisesincreasing the transmit power limits in both the over-limit modem and aninactive one of the N modems when an aggregate transmit power of all ofthe N modems is less than the aggregate transmit power limit by apredetermined amount.
 11. The method of claim 10, further comprising:(e) activating the inactive modem, whereby the inactive modem becomesactive; and (f) repeating steps (b), (c) and (d).
 12. The method ofclaim 9, wherein step (b) comprises scheduling active ones of the Nmodems to transmit their data, the method further comprising, prior toincreasing the transmit power limit of the over-limit modem in step (d):determining an aggregate transmit power for all of the N modems, whereina difference between the aggregate transmit power and the aggregatetransmit power limit represents an aggregate transmit power margin ofthe data terminal; and increasing the aggregate transmit power marginwhen the aggregate transmit power margin is insufficient to permit anincrease in the transmit power limit, and correspondingly the transmitpower, of the over-limit modem.
 13. The method of claim 12, wherein saidstep of increasing the aggregate transmit power margin comprisesincreasing the aggregate transmit power margin when the aggregatetransmit power is greater than or equal to the aggregate transmit powerlimit.
 14. The method of claim 11, wherein said step of increasing theaggregate transmit power margin comprises: deactivating an active one ofthe N modems having a greatest transmit power among the N modems; anddecreasing the transmit power limit in the modem deactivated in step(e)(i).
 15. The method of claim 14, wherein, as a result of step (d),all of the transmit power limits, when combined together, are less thanor equal to the aggregate transmit power limit, and each individualtransmit power limit is greater than a corresponding individual modemtransmit power.
 16. In a data terminal constrained to operate within anaggregate transmit power limit, the data terminal including N wirelessmodems having their respective transmit outputs combined to produce anaggregate transmit output, the modems having individual transmit powerlimits to limit their respective transmit powers, the modems reportingrespective transmit power estimates, a method of deriving the individualtransmit power limits, comprising: (b) determining an aggregate transmitpower encompassing all of the N modems; (b) deriving an aggregatetransmit power margin based on a difference between the aggregatetransmit power and the aggregate transmit power limit; and (c) dividingthe aggregate transmit power margin among the N modems to produce, foreach of the N modems, an individual transmit power limit that is greaterthan the corresponding transmit power estimate for each modem.
 17. Themethod of claim 16, wherein step (c) comprises dividing the aggregatetransmit power equally among the N modems.
 18. The method of claim 16,further comprising, prior to step (a): producing a corrected transmitpower estimate from each transmit power estimate using a correspondingpredetermined, modem gain correction factor; and performing steps (a)and (c) using the corrected transmit power estimates.
 19. An apparatusfor controlling a wireless terminal constrained to operate within anaggregate transmit power limit, the wireless terminal including Nwireless modems having their respective transmit outputs combined toproduce an aggregate transmit output, comprising: means for establishingan individual transmit power limit in each of the N modems; means forscheduling each of a plurality of the N modems to transmit respectivedata; means for receiving a respective, reported transmit power estimatefrom each of the N modems; and means for adjusting the individualtransmit power limits in at least some of the N modems based on theaggregate transmit power limit and the respective transmit powerestimates from the N modems, to cause each individual transmit powerlimit to track a corresponding individual modem transmit power.
 20. Theapparatus of claim 19, wherein the adjusting means comprises means foradjusting the individual transmit power limits such that when the Nindividual transmit power limits are combined into a combined transmitpower limit, the combined transmit power limit is less than or equal tothe aggregate transmit power limit, and each individual transmit powerlimit is greater than the corresponding individual modem transmit power.21. The apparatus of claim 20, wherein the means for scheduling, themeans for receiving, and the means for adjusting perform theirrespective functions periodically to cause the individual transmit powerlimits to track changes in the corresponding modem transmit powers overtime.
 22. The apparatus of claim 19, further comprising means forestablishing an individual wireless communication link between each ofthe N modems and a remote station, each communication link including aforward link and a reverse link.
 23. The apparatus of claim 22, whereineach wireless communication link is a Code Division Multiple Access(CDMA) communication link.
 24. The apparatus of claim 19, wherein theadjusting means comprises: means for deriving new individual transmitpower limits for the N modems; and means for updating the at least someof the N modems with corresponding ones of the new individual transmitpower limits.
 25. The apparatus of claim 19, wherein the adjusting meanscomprises: means for determining an aggregate transmit power for all ofthe N modems; means for determining an aggregate transmit power marginbased on a difference between the aggregate transmit power and theaggregate transmit power limit; and means for dividing the aggregatetransmit power margin among the N modems to produce for each of the Nmodems an individual transmit power limit that is greater than acorresponding modem transmit power.
 26. The apparatus of claim 25,wherein: the adjusting means further comprises means for producing acorrected transmit power estimate from each transmit power estimateusing a corresponding predetermined, modem gain correction factor; andthe means for determining an aggregate transmit power comprises meansfor determining the aggregate transmit power using the correctedtransmit power estimates.
 27. The apparatus of claim 19, furthercomprising: means for determining an over-limit one of the N modems,wherein the adjusting means comprises means for increasing the transmitpower limit of the over-limit modem.
 28. The apparatus of claim 27,wherein: the scheduling means comprises means for scheduling active onesof the N modems to transmit their respective data; and the adjustingmeans comprises means for increasing the transmit power limits in boththe over-limit modem and an inactive one of the N modems when anaggregate transmit power of all of the N modems is less than theaggregate transmit power limit by a predetermined amount.
 29. Theapparatus of claim 28, further comprising: means for activating theinactive modem, whereby the inactive modem becomes active, wherein thescheduling means, the receiving means, and the adjusting means repeattheir respective functions over time.
 30. The apparatus of claim 27,wherein the scheduling means comprises means for scheduling active onesof the N modems to transmit their data, the apparatus furthercomprising: means for determining an aggregate transmit power for all ofthe N modems, wherein a difference between the aggregate transmit powerand the aggregate transmit power limit represents an aggregate transmitpower margin of the wireless terminal; and means for increasing theaggregate transmit power margin when the aggregate transmit power marginis insufficient to permit an increase in the transmit power limit, andcorrespondingly the transmit power, of the over-limit modem.
 31. Theapparatus of claim 30, wherein the means for increasing the aggregatetransmit power margin comprises means for increasing the aggregatetransmit power margin when the aggregate transmit power is greater thanor equal to the aggregate transmit power limit.
 32. The apparatus ofclaim 31, wherein the means for increasing the aggregate transmit powermargin comprises: means for deactivating an active one of the N modemshaving the greatest transmit power among the N modems; and means fordecreasing the transmit power limit in the deactivated modem.
 33. Theapparatus of claim 32, wherein, as a result of the adjusting meansadjusting the transmit limits, all of the transmit power limits, whencombined together, are less than or equal to the aggregate transmitpower limit, and each individual transmit power limit is greater than acorresponding individual modem transmit power.
 34. An apparatus forderiving modem transmit limits in a wireless terminal constrained tooperate within an aggregate transmit power limit, the wireless terminalincluding N wireless modems having their respective transmit outputscombined to produce an aggregate transmit output, the modems havingindividual transmit power limits to limit their respective transmitpowers, the modems reporting respective transmit power estimates,comprising: means for determining an aggregate transmit powerencompassing all of the N modems; means for deriving an aggregatetransmit power margin based on a difference between the aggregatetransmit power and the aggregate transmit power limit; and means fordividing the aggregate transmit power margin among the N modems toproduce, for each of the N modems, an individual transmit power limitthat is greater than the corresponding transmit power estimate for eachmodem.
 35. The apparatus of claim 34, wherein the dividing meanscomprises dividing the aggregate transmit power equally among the Nmodems.
 36. The apparatus of claim 34, further comprising: means forproducing a corrected transmit power estimate from each transmit powerestimate using a corresponding predetermined, modem gain correctionfactor, wherein the determining means uses the corrected transmit powerestimates to determine the aggregate transmit power.